Fibronectin (to be referred to as FN hereinafter) is a huge glycoprotein having a molecular weight of about 250,000, which exists in an animal blood, on the surface of a cultured cell or in an extracellular matrix of a tissue, and is known to have various functions. Its domain structure is divided into seven, and three types of similar sequences are contained in its amino acid sequence and the entire sequence is constituted by repetitions of these respective sequences. The three types of the similar sequences are called type I, type II and type III. Among them, the type III is constituted from 71 to 96 amino acid residues and the ratio of identity of these amino acid residues is from 17 to 40%. Fourteen of type III sequences are contained in FN, and among these, the 8th, 9th and 10th sequences (to be referred to as III-8, III-9 and III-10, respectively, hereinafter) are contained in a cell-binding domain, and the 12th, 13th and 14th sequences (to be referred to as III-12, III-13 and III-14, respectively, hereinafter) are contained in a heparin-binding domain. Also, a VLA (very late activation antigen)-5 binding region is contained in the III-10, and the core sequence thereof is RGDS. In addition, a region called IIICS exists at the C terminal side of the heparin-binding domain. A region called CS-1 having a binding activity for VLA-4, which consists of 25 amino acids, exists in the IIICS.
As described above, FN has various physiological activities such as adhesion to cells, signal transduction and the like. Similar to the case of general physiologically active substances, it is advantageous to use a specific antibody in studying these physiological activities. A monoclonal antibody which reacts with FN has already been reported in Patent Document 1 (JP-B-6-44877).
On the other hand, an FN fragment consisting of a functional domain of FN or a part thereof has been prepared in Non-patent Document 1 (J. Biochem., 1991, Vol. 110, No. 2, pp. 284-291). It is known that a certain FN fragment improves the efficiency of gene transfection using a retrovirus vector into a hematopoietic stem cell, see Non-patent Document 2 (Human Gene Therapy, 1997, Vol. 8, No. 18, pp. 2193-2206) and Non-patent Document 3 (Nature Medicine, 1996, Vol. 2, pp. 876-882). In addition, a culturing method in which an FN fragment is added to a medium for immune cells is reported in Patent Document 2 (WO03/016511). Thus, FN fragments are used for addition to a cell culture medium, immobilization onto a cell culture container and the like.
[Patent Document 1] JP-B-6-44877
[Patent Document 2] International Publication No. WO03/016511
[Non-patent Document 1] J. Biochem., 1991, Vol. 110, No. 2, pp. 284-291
[Non-patent Document 2] Human Gene Therapy, 1997, Vol. 8, No. 18, pp. 2193-2206
[Non-patent Document 3] Nature Medicine, 1996, Vol. 2, pp. 876-882